1. Field of the Invention
The present invention relates to a motor-driving device of an electric caulking gun and more particularly to a motor-driving device of electric caulking gun capable of maintaining a preset caulk discharge rate.
2. Description of the Related Art
Powered by electricity, a conventional electric caulking gun drives a push rod through a motor to repel the caulk in a caulk tube for the purpose of sealing up gaps and cracks. In consideration of different operation modes or demands for different caulk discharge rates, every conventional electric caulking gun is equipped with a variable speed mechanism to vary the speed of the push rod upon repelling the caulk in the caulk tube so that caulk in the caulk tube can be discharged from the tube nozzle at different speeds.
Despite the variable speed mechanism for adjusting the speed of the push rod to further vary the caulk discharge rate and speed, conventional electric caulking guns fail to evenly dispense caulk on a work piece upon overlapping, turning or gradually stopping discharging the dispensed caulk on the work piece. The issue of unevenly dispensed caulk is caused because the variable speed mechanism of the conventional electric caulking guns is unable to quickly adjust the caulk discharge speed during the caulk dispensing process.
Also, if the tube nozzle is blocked by foreign matter and the caulk cannot be smoothly discharged, if the caulk remained at the tube nozzle is hardened because of prolonged air contact, or if the formula or ingredients of caulk vary from manufacturer to manufacturer and the caulk discharge speed or rate also varies from caulk to caulk because of different resistance to discharged caulk arising different viscosity of caulk, operational inconvenience is caused as the caulk discharge rate is unsteady and users must manually remove the blockage at the tube nozzle or adjust the speed of the variable speed mechanism according to the ingredients of the selected caulk.